Add the flour, 1 ½ teaspoons sugar, and ½ teaspoon salt to a medium mixing bowl. Whisk to mix.
Take the stick of the frozen butter and grate it into the flour mixture. Stir frequently so that the butter doesn’t clump.
Add the water, a tablespoon at a time, until the dough starts to come together.
Knead for a minute to ensure a good pie dough texture, then form a disk.
Wrap in plastic wrap and refrigerate for 30-60 minutes.
BAKE PIE CRUST:
Preheat the oven to 400°F.
Remove the dough from the refrigerator and roll it out (to about 1/8” thick).
Drop it into a 9” pie dish, then flute the edges to form a pretty shape (it also helps keep the dough in place while baking.
Blind bake the pie crust for 20 minutes (using pie weights or whatever you use), then remove and continue to bake for 5-10 minutes.
Finally, remove it from the oven and allow it to cool completely.
MAKE PUMPKIN LAYER::
Add sugar, gelatin, pumpkin pie spice, and salt to a medium saucepan. Whisk to mix well.
Add the pumpkin puree, egg yolks, and milk to another bowl. Whisk until smooth, then pour into the saucepan with the sugar mixture. Whisk well, and then turn the burner to medium heat.
Bring it to a bubble, and then keep it bubbling for about 4-5 minutes. Then, remove from the heat and cool to room temperature.
In a large bowl, combine egg whites and cream of tartar.
Beat until soft peaks form.
Fold the cooled pumpkin mixture into the egg whites using a soft spatula. Fold carefully until combined.
Pour pumpkin mixture into the cooled pie crust and smooth into an even layer.
Place in the refrigerator for at least 6 hours, overnight preferably.
MAKE WHIPPED CREAM:
Beat the whipping cream until stiff peaks form.
Decorate the top of the pie with whipped cream as you please.
TO FINISH:
Dust the top of the pie with pumpkin pie spice (optional).